Expert explains ‘10% speed camera margin’ as warning issued over speeding
Drivers are also being advised about the difference between mobile and fixed cameras as well as common speeding myths
10:00, 27 Jul 2025
A motoring expert has shared advice about speed cameras(Image: Getty Images/iStockphoto)A motoring expert has shed light on how speed cameras work and whether there's a 10% margin for speeding fines. They have also outlined the law and explained what speed actually triggers a camera.
With almost 350 people killed on the UK's roads each year, speed enforcement remains a key part of road safety. Now car valuation experts at BigWantsYourCar.com[1] are warning drivers not to rely on myths or guesswork when it comes to speed limits.
A spokesperson said: "We regularly speak with drivers who think there's a guaranteed buffer.
But the truth is, as soon as you exceed the speed limit, you're technically breaking the law.[2]" More information is given below.
How speed cameras actually work
Speed cameras work using radar or road markings to monitor a vehicle's speed and capture evidence of any offence[3]. While older cameras used film, most modern devices are fully digital and can even track your average speed over many miles.
"Not all cameras flash anymore," explains the BigWantsYourCar.com expert. "Some operate silently, and some mobile units are manually operated - so relying on a flash as a warning is a risky game."
These digital systems record:
Article continues below- Vehicle speed
- Time and location of the offence
- Vehicle registration
- Road speed limit
In some cases, they even capture a clear image of the driver[4] and passenger.
What speed triggers a camera?
Contrary to common belief, there's no universal "10% + 2mph" rule baked into law. "The idea that you're safe doing 35mph in a 30 zone is one of the biggest myths we hear," the spokesperson says. "Technically, you're liable for a fine the moment you go even 1mph over the limit."
While the National Police Chiefs' Council (NPCC) does recommend a "10% plus 2" margin to allow for officer discretion, this is not a legal threshold and can vary depending on the enforcement area or the officer reviewing the case.
Mobile cameras vs fixed cameras
Fixed cameras typically have a set trigger speed, though the exact threshold is rarely published. Mobile cameras, on the other hand, are operated manually - and decisions to issue fines can depend on how far over the limit you are and the circumstances.
Article continues below"Mobile speed units are particularly unpredictable," says BigWantsYourCar.com. "They're often deployed in accident-prone zones, so officers tend to take a tougher stance."
Don't risk it
With speeding fines ranging from fixed penalties to points on your licence and even court appearances, the best strategy is simple. "Don't gamble with the grey area," warns the BigWantsYourCar.com team. "If you're even slightly over the limit, you're putting your licence, insurance, and safety at risk.
No journey is worth that."